Temperature sensors are commonly used to measure the ambient temperature. However, implementing a temperature sensor within an electronic device for the purpose of measuring ambient temperature poses challenges. Electronic devices generate heat which affects the measurements made by the temperature sensor. If the objective is to measure the ambient temperature, such as the room temperature, and not the temperature of the electronic device within which the temperature sensor is mounted, then the temperature sensor either must be isolated from the heat generating portion of the electronic device, or the sensed temperature must be adjusted to account for that portion attributable to the heat generation of the electronic device. Adjusting the sensed temperature measurements to compensate for the internal heat generation is difficult as the amount of heat generated within the electronic device varies based on current power being consumed, such as the amount of processing power being used, and other operational aspects of the device. Orientation of the device, such as standing up or laying down, and the relative position of the temperature sensor may also influence the temperature readings since heat rises.
The location of the temperature sensor on or within the electronic device influences the measured temperature results. If the temperature sensor is positioned within the housing of the electronic device, then the temperature sensor is exposed to the heat generating components of the electronic device, thereby influencing the sensed temperature measurements. Further, there is little airflow into the housing for measuring of the ambient air temperature outside the housing. As such, positioning the temperature sensor within the electronic device housing for the purpose of measuring ambient temperature is not effective.
The temperature sensor can alternatively be positioned on an outer surface of the electronic device. However, typical housings are made of heat conducting material, such as metal, and therefore conduct heat generated from within the electronic device, again influencing the sensed temperature measurements. Also, many users of handheld electronic devices, such as cellular telephones, use protective cases over the device to protect from damage. Such cases block a temperature sensor positioned on the external housing. Some electronics devices have a surface made of a non-conductive material, such as a display surface of a cellular telephone having an exposed glass layer. When the temperature sensor is placed on the external side of the non-conducting glass layer, the glass layer insulates the temperature sensor from the heat generating components internal to the device. This insulation reduces the affects of the heat generating components on the sensed temperature measurements.
Positioning the temperature sensor on the external side of the glass layer provides insulation from the heat generating components within the electronic device. However, simply placing the temperature sensor on the exposed surface of the glass layer is not amenable for protecting the sensor as the sensor protrudes from the surface, exposing the sensor to potentially damaging contact. Additionally, temperature sensors are typically wired to electronic components to receive power and to transmit the measured sensed temperatures. The temperature sensor is wired to the electronic components used to operate the electronic device, which are also the heat generating components. The wired connection is heat conducting, and as such heat is conducted from the heat generating components to the temperature sensor via the wired connection. Providing a wired connection through the glass cover also poses manufacturing difficulties.
Accordingly, how can the temperature sensor distinguish between the heat generated by the electronic device and the ambient temperature? Further, in order to measure the ambient temperature, the temperature sensor needs to be exposed to the ambient air. How can the temperature sensor be assembled into the electronic device such that the temperature sensor is sufficiently exposed to the ambient air? Still further, the temperature sensor must be insensitive to errors due to device orientation, humidity, pressure, and other environmental and device related factors that may impact the temperature sensor measurement.